The present invention relates to the use of single and multi-layer films or foils containing an adhesive comprising ethylene vinyl alcohol (EVOH) to adhere to and securely seal glass containers such that the seals will remain intact under storage conditions of high temperature and humidity.
The use of ethylene vinyl alcohol (EVOH) as an oxygen barrier layer in film laminates especially as part of a barrier layer in food packaging is well known in the art. Typically, the laminate is in the form of an inner moisture barrier layer, an adhesive layer, EVOH, another adhesive layer and an outer moisture barrier layer. It is usually necessary for the laminate to have this structure so as to maintain the EVOH layer dry since the EVOH will not act as an oxygen barrier once exposed to water. The sealant layer in such laminates must also function as a barrier to the product to keep components of the product from wicking through the sealant layer and adversely affecting the sealant bond and to prevent those components from adversely affecting other lamination bonds of a multi-layer material or the graphics of a printed laminate material. When EVOH is used as an oxygen and moisture barrier layer as in the prior art, product components can still migrate into the layers positioned between the product and the EVOH layer. Similarly, polymeric components of the sealant and adhesive layers may migrate from those layers into the product.
The use of EVOH films in contact with food products are known. One example of a laminate barrier structure for a food container having an inner layer of EVOH in contact with the food is disclosed in U.S. Pat. No. 4,997,004. That patent describes a multi-layer barrier structure having a layer of EVOH next to the food, an adhesive layer, a moisture barrier layer, a further EVOH layer and another moisture barrier layer. The laminate is either applied to cardboard stock to make a carton or used as part of a plastic carton. The use of EVOH films in contact with food products are known. One example of a laminate barrier structure for a food container having an inner layer of EVOH in contact with the food disclosed in U.S. Pat. No. 4,997,004. That patent describes a multi-layer barrier structure having a layer of EVOH next to the food, an adhesive layer, a moisture barrier layer, a further EVOH layer and another moisture barrier layer. The laminate is either applied to cardboard stock to make a carton or used as part of a plastic carton. The patent discloses that the EVOH layer next to the food precents xe2x80x9cscalpingxe2x80x9d of flavor by absorption of essential oils from the food. The EVOH layer between the mousture barrier layers is used as an oxygen barrier to prevent oxygen from entering the package. The patent discloses that the EVOH layer next to the food prevents xe2x80x9cscalpingxe2x80x9d of flavor by absorption of essential oils from the food. The EVOH layer between the moisture barrier layers is used as an oxygen barrier to prevent oxygen from entering the package.
It is well known that if an EVOH layer is used as an oxygen barrier, the EVOH layer must be kept in an anhydrous state to maintain the effectiveness of the oxygen barrier. U.S. Pat. No. 4,792,484, describes the use of a granular drying agent in a layer of EVOH to maintain the anhydrous state. The EVOH can then be used as the oxygen barrier layer in a multi-layer package and especially as part of a multi-layered film useful in packaging retorted food.
U.S. Pat. Nos. Re. 32,927; 4,632,271; and 4,793,510 disclose a metal can with a resealable top having a rubber gasket as part of the sealing element. The rubber gasket is disclosed as having a surface coating of waxes and lacquers to improve compatibility and sealability with the metal surface. Polyvinylidene chloride (PVDC) or ethylene vinyl alcohol (EVOH) are suggested for reducing gas transmission if necessary.
The present invention relates to the use of ethylene vinyl alcohol films as an adhesive to glass surfaces. Such films can be incorporated in laminates with various physical properties according to the different layers of the laminate. The use of ethylene-vinyl alcohol films as an adhesive is particularly advantageous because the films are non-tacky and easy to handle compared with normal food grade adhesives.
A primary objective of the invention is to provide a novel laminate film that can be heat and pressure sealed to a glass container using a food grade adhesive. The adhesive film is intended to be used as a inner layer, or safety sealing layer, for glass food containers, such as open-mouthed glass jars. The film adhesive layer not only withstands moisture, but also the elevated temperatures associated with the shipping and warehousing of canned foods without failure. This is accomplished according to the invention by the use of a saponified ethylene vinyl acetate copolymer composition (referred to hereinafter as EVOH) wherein at least one EVOH layer is adjacent to the rim or lip of the glass container to be sealed.
A further object of the invention is to provide a laminate film wherein the film layer adjacent to the glass functions as an adhesive to securely and safely seal the laminate film to the glass.
A further objective of the invention is to provide a laminate film that can be used as an adhesive label for labeling glass containers and to thus avoid the use of liquid or other types of label adhesives.
With the foregoing and other objects, advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several views illustrated in the drawings.